Our long term objective is to understand the neural mechanisms underlying aspects of language. Considerable progress has been made in understanding aspects of the processing of words and word strings though cognitive psychological studies and lesion-behavior studies. Positron emission tomographic (PET) studies of blood flow (BF) change in the brains of normal humans represent another too for approaching these issues, and will be used to address questions about the identification and contribution of specific brain areas activated during the performance of tasks related to different aspects of word and word-string processing. The proposed research will focus on three related sets of issues: 1) to build on the results of previous single word processing PET experiments performed in this laboratory focusing on how different areas are activated by different classes of words (high-vs. low- frequency, regularly-vs. irregularly spelled, etc.) and different types of subword units (rapidly modulated sounds,e.g. stop consonants,vs. steady state sounds, e.g. some vowels) to make more precise description of types of processing carried out by the different areas; 2) to identify areas activated during tasks that necessitate short term buffering of strings of words, areas that may be related to aspects of verbal working memory processes; and 3) to assess the areas activated during the performance of tasks that require automatic or intentional syntactic and semantic analyses on different types of word strings hoping to identify candidate structures that perform some of the processes related to these analyses. While the main purpose of the experiments is to further our basic understanding of mechanisms underlying aspects of language, there are clinical implications as well. There could be diagnostic utility in the ability to more clearly define structure-function relationships in the brain, and the ability to determine, in individual patients, the anatomical location of areas related to important functions will allow for the avoidance of these areas during neurosurgical procedures.